Structural tower



Aug. 25,1931. L. A. PRESCOTT ET AL 1,320,156

STRUCTURAL TOWER Filed July 25, 1929 2 Sheets-Sheet 1 INVENTOR5 A. 9 W i 62; W wuib Aug, 25, 1931. 1.. A. PRESCOTT ET AL STRUCTURAL TOWER Filed July 25. 1929 2 Sheets-Sheet 2 Patented Aug. 25, 1931 UNITED STATES PATENT OFFICE LYLE A. PRESCOTT AND IRA W. MAB-SHALL, 0F PITTSBURGH, PENNSYLVANIA, ASSIGN- ORS TO BLAW-KNOX COMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION "on NEW JERSEY Application filed July 25,

Our invention relates to structural towers, and more particularly to transmission towers and ground wire supportstherefor. In designing electrical transmission lines it is necessary to curve the lines in following the topography of a section of country or-in following a right of way. lVhenever a curve exists in a transmissionline, the electrical conductors, which are suspended by strings of insulators from cross arms, assume a position to oneside or the other of a vertical line passing through their points of support on the cross arms. The conductors move toward the inside of the curve relative to their points of support on the cross arms. In many transmission lines three conductors constituting a three phase circuit are disposed one above the other on each side of the tower, thereby constituting a double circuit transmission line. i i

j The lengths of the cross arms and the lengths of the strings of suspension insulators are so designed that the conductors are r maintained at safe distances from the body or 'basket of the tower at all times.

In manytransmissionlines of this general character a ground wire is suspended from cross arms above the uppermost electrical conductor in each circult and at a distancebeyond or outside of the conductors,

thereby [constituting a partial electrical shield for the current carrying conductors against lightning discharges and induced currents. The ground wires also are electrically' connected to each tower. In four wire systems, the ground wire is sometimes used as a neutral return wire. lVhere groundwires are placed above a circuit on each side of a tower, the two ground Wires and the tops of the towers outline an electrical field which exerts considerable influence in preventing lightning discharges to the conductors.

It is desirable that the ground wire be as nearly directly above the power conductors as practicable at all points therealong and, accordingly, the horizontal projection of the ground wire beyond the position of the electrical conductors should be substantially a STRUCTURAL TOWER I 1929. Serial No. 380,820."

constant value regardless of whether each conductor hangs directly below its point of attachment to a cross arm or whether it is,

apex of every angle in a transmission relative to the tower so that'the positions of the ground wires can be shifted in accordance with the horizontal displacement of the conductors at "each tower. As the conductors at the outside of a curve are shifted inwardly by the same amountthat the inside conductors are shifted outwardly at any angle in the transmission line, inward shifting of the cross arm and the ground wire on the outside of the curve moves the ground wire on the opposite side of the tower outwardly the same distance, which leaves the ground wires at both'sides of the tower insubstantially the same relative positions with respect to the conductors disposed therebeneath.

The accompanying drawings illustrate a present preferred embodiment of the invention, in which; Figure l is an elevational view of a portion of a structural tower, showing the positions of the conductors in a straight section of the transmission line,

Figure 2 is a similar view'showing the relative positions of the ground wires and conductors when the transmission line curves to the left,

Figure 3 is a similar view of the ground wires and conductors when a curve ismade to the right, I

Figure 4: is a diagrammatic view in plan showing the relative positions of the conductors and, groundwires under conditions of a straight transmission line, a left curve and a right curve,

Figure 5 is a detail view showing the attachment of the ground wire support to the lJtLSXGt or body of the tower, and

Figure 6 is an end view of a cross arm showing the attachment of the ground wire thereto.

Referring to the drawings, a structural tower l in the form of a transmission tower comprises abody or basket port-ion 2, to which structural cross arms eland 5 are attached for carrying electrical conductors. In practice, three cross arms usually projectfrom each side of the basket 2 for supporting the three conductors of a three phase circuit. The cross arm is of substantially the same construction as the cross arm i and a third cross arm is disposed on the basket 2 below the cross arm 5. Conductors 6 and 7 are suspended from the cross arm l by strings of suspension insulators 8 and 9 respectively.

The insulator strings 8 and 9 have some flexibility to permit lateral movement of the conductors relative to the basket 2. The upper ends of the insulator strings S and 9 are anchored at substantially the outer ends of the cross arm 4:. The construction of the basket 2, the cross arm at and insulator strings S and 9 may be of any general type, as is well understood in the art.

For controlling induced electrical fields adjacent the conductors 6 and T, and especially for preventing lightning discharges from striking the conductors, ground wires 10 and 11 are suspended from a cross arm 12 disposed above the cross arm 4i. The ground wires 10 and 11 are disposed outside of the conductors 6 and 7 -\vith respect to the tower basket 2.

In generah the horizontal projection of the ground wire beyond the electrical conductors protected thereby should remain a constant regardless of curves in the transmission line. As the conductors 6 and T are pulled inwardly of every curve in the transmission line, and as most transmission lines make both right and left curves, the ground wires 10 and 11 must be correspondingly shifted.

By providing the cross arm 12 for the ground wires with a considerable number of openings 14, it is possible to shift the support laterally of the basket 2 in accordance with the direction of displacement of the conductors at each curve, thereby eliminating the need for a specially constructed tower at the apex of each angle. Clamping bolts 15 are inserted through the openings 1d and engage structural elements of the basket 2 for securing the cross arm 12.

Referring to l igure 2, the conditions encountered in a left curve are illustrated The conductors 6 and 7 are moved to the left by equal amounts and the cross arm 12 is shifted to the left far enough so that the ground wires 10 and 11 have the correct overhanging with respect to the conductors (3 and 7, respectively. The distances between the ground wires 10 as d 11 and the conductors 6 and 7, respectively, remain substantially the same except for the small differences caused by the lifting of the conducti'irs 6 and '7 relative to their supports on the cross arm at when swinging about the points of attachment of the insulator strings S and 9, respectively.

As the horizontal displacement of the conductors 6 and 7 the same, the conductor 6 moves inwardly toward the basket and the conductor 7 moves outwardly from the basket. The movement of the cross arm 12 to the left of the basket 2 maintains the ground wires 10 and 11 in their proper positions relative to the conductors (5 and 7, respectively.

Referring to Figure 3, the relative posi tions of the parts under conditions of a right hand curve in the transmission line are illustrated. In this case the conductor- 7 swings in towara'l the basket 2 and the conductor (3 swings away thcrefron'i. The cross arm 12 is correspondingly shifted to the right for maintaining the ground wires 10 and 11 in an overhanging position relative to the conductors 6 and 7, respectively.

'lef rring to Figure l, the normal positions of the conductors and ground wires are shown in solid lines with the cross arm 12 disposed centrally of the tower. This is the normal position of the conductors and ground wires when a transmission line is straight. The positions of the ground wires under conditions of a curve to the left in a transmission line are shown by dash and dot lines at the extreme left of Figure l, and by the second line to the right of the tower basket 2.

The positions of the ground wires and conductors under conditions of a right turn in the transmission line are shown at the extreme right of Figure 4, and by the first and second lines "to the leftof the basket As shown by the reference characters A, the horizontal distance between the ground wires and conductors is maintained the same under all conditions by merely shifting the position of the cross arm. 12. This is in part possible by reason of the fact that the strings of insulators 8 and 9 turn about their anchors in the same direction through equal angles under any condition of curvature providcd the strings are of the same length and the tension in the electrical conductors supported thereby is substantially the same.

Referring to Figures 5 and G, the cross arm 12 is constituted by channel irons 16 which are secured along their upper edges by cleats 17, and along their lower edges by a plate 18. The channel irons 16 may be secured to the cleats 17 and the plate by any one of the common methods such as bolting, riveting and/or welding. The ground. wires 10 and 11 are supported by hooks 19 which engage U bolts 20 extending upwardly through openings 21 in the plate 18. The hooks 19, bolts 20 and plate 18constitute ground connections for the ground wires 10 and 11, which connections are complete I through the frame work of the tower to the ground. The towers are also electrically connected to each other and are thereby maintained at ground potential, even though some of the towers may have. a better electrical connection to ground than others. Clamping nuts 22 secure the bolts 20 in the plate. a

The-cross arm 12 is supported by horizontally extending angle irons 24 supported by vertically extending struts 25,-constituting the corners of the basket .2. Some of the clamping bolts 15 extend through the an le irons 24. Bracin arms 26 extend u wardly in a converging direction to plates 27 through openings in which other clamping bolts 15 extend. When it is desiredto I adjust the position of the cross arm 12, the

bolts 15 are removed and the crossarm is moved laterally of the basket 2 to the desired position when the bolts 15 are inserted in other'openings 14 for clamping the cross vention, it will be understood that the same is not limited thereto, but may be otherwise embodied without departing from the scope of the appended claims.

We claim: I

1. A structural tower comprising a body, a fixed supportfor a suspended electrical power conductor adapted to occupy different positions relative to said body, and an ad 'justable support for a ground conductor, whereby the ground conductor may be maintained in substantially a definite spaced remounted support for a ground wire, whereby the ground wire may be maintained in substantially a definite spaced relation to the conductor in its different positions.

3. A structural tower comprising a body,

a support for an electrical conductor, and an adjustably mounted support for a ground wire above said first-mentioned support.

1. A structural tower comprising a body, a cross arm for supporting electrical conductors on oppositesides of the tower, and an.

adj ustably mounted support above said cross arm for ground wires carried on opposite sides of the tower.

5. A structural tower comprising an adjust-ably mounted support for a ground wire at the top of the tower and extending laterally thereof.

6. A structural tower comprisinga cross arm-for supporting an electrical conductor, and an adjustably mounted support for a ground wire disposed above said cross arm.

7. A structural tower comprising an adjustably mounted support for a ground wire disposed at substantiallythe top of the tower and fixed supports. power conductors therebelowL 8. A structural tower comprising a cross arm for supporting an electrical conductor, and an adjustable support for a ground wire extending outwardly of the tower beyond said conductor. V p

9. A structural towercomprising a cross arm for supporting conductors carried thereby on opposite sides of the tower, and an adjustably mounted cross arm for supporting ground wires in an overhung relation relative to said conductors.

10; A structural tower] comprising a ground wire support adapted to occupy different positions on the tower.

11. A ground wire support adjustable laterally of the tower. v

12. A structural tower comprising a ground wire supportprojectible for different distances on opposite sides of the tower.

13. A structural tower comprising a ground wire support shiftable bodily relative to the tower.

14. A structural tower comprising a body, and a ground wire support having holes for the reception of clamping bolts, where by the ends of the groundwire support may be projected different distances from the tower body.

In testimony whereof we have hereunto set out. hands. I

LYLE A. PRESCOTT. IRA W. MARSHALL.

structural tower comprising a 

